inconsistent Torbutton behavior when control port config is missing
Torbutton is inconsistent in how it handles missing control port configuration. Some code disables features if one or more pieces of information needed to access the control port are missing (e.g., New Identity is disabled if there is no control port socket or TCP port). In other cases, defaults are used (e.g., the circuit display uses a default port of 9151). We should decide what behavior we want and modify the code to be consistent with it.